In a mobile communication system the data rate can be adapted dynamically for efficiency reasons. The power of the transmitted signal also changes due to the data rate as every successfully transmitted bit must be paid for with a certain amount of transmitted energy. In a transmitter of a mobile communication system channel coding is usually employed, providing bit redundancy for the purpose of error protection. Channel coding can be employed with timely varying code rates. As very high code rates result in very low redundancy a problem arises in particular for certain modulation schemes when any amplitude variation is present in the transmitted signal.